A new fluorescent chemosensor for F− based on inhibition of excited-state intramolecular proton transfer

New fluorescent chemosensor 1 with two amidoanthraquinone groups (1-AAQs) at the lower rim of p-tert-butylcalix[4]arene has been synthesized. The significant changes of absorption and fluorescence bands show that chemosensor 1 is selective toward fluoride ion (F−) over other anions such as Cl−, Br−, I−, CH3COO−, H2PO4-, HSO4-, and OH−. The ESIPT process of 1 is inhibited by the fluoride-induced H-bonding followed by deprotonation of NH of the 1-AAQ.